Specific objectives of this study are: 1) To determine whether high-dose acyclovir vs. vidarabine therapy can further decrease morbidity and mortality of CNS or disseminated neonatal HSV infection both acutely and on long-term follow-up. 2) To determine if high dose acyclovir chemotherapy is safe and tolerated in the newborn, the following will be monitored- a) biochemical and bone-marrow parameters of host function (SGOT, BUN, creatinine, CBC with differential, platelet count, and urinalysis). b) host antibody response (total HSV antibodies by ELISA and antibodies to specific polypeptides.) c) Adverse effects both acutely and on long-term follow-up. 3) To determine if resistance to antiviral medication develops 4) To amplify disease classification for babies with neonatal HSV infection for purposes of predicting prognosis 5) To determine whether there is a change in viral excretion patterns in high-dose acyclovir vs. vibaridine therapy 6) To determine whether antigens and antibodies specific for HSV glycoproteins within the CSF predict long-term neurologic outcome 7) To determine whether specific antigens and antibodies in the CSF appear late after treatment and are indicatiove of insidious reactivation of virus in the brain.